I am using the UV channel to store vertex data in the range of about -1.5 to 6.5 on U and -0.3 to 4 on V. When I bring the geometry into unreal and set up the material I get unexpected results for the V channel only, U is fine.
I can fix it by selecting “Un Mirror V” in the TexCoord node.
I would just like to know what is happening so I can be sure I’m applying the right fix. Unreal is doing something to the UVs on import for this error to occur but I don’t understand why it is happening now as I have imported many models with regular texture UVs and never had to use this option.